MACHINE TOOL FOR GRINDING DISCS

Abstract

Methods and machine tools for grinding discs. The machine tool comprises two grinding units with respective grinding spindles on which grinding wheels are arranged and a disc unit that comprises a disc spindle on which the disc to be grinded is arranged. The rotation axes of the grinding spindles are perpendicular to the disc spindle rotation axis. The grinding wheels comprise respective grinding surfaces which are perpendicular to the rotation axis of the disc spindle. The grinding surfaces have a width that is equal or greater than the width of the main surfaces of the disc. The two grinding units are configured to simultaneously move relative to the disc unit in an axis that is parallel to the rotation axis of the disc spindle and in opposite directions such that, in use, the grinding surfaces simultaneously contact opposite surfaces of the disc to grind them down.

Claims

1. A machine tool for grinding discs, comprising: a first grinding unit comprising a first grinding spindle having at least one first grinding wheel arranged thereon and a first motor assembly to rotatably actuate the first grinding spindle; a second grinding unit comprising a second grinding spindle having at least one second grinding wheel arranged thereon and a second motor assembly to rotatably actuate the second grinding spindle; at least one disc unit comprising a disc spindle on which the disc to be grinded is to be arranged and a third motor assembly for rotatably actuating the disc spindle; characterized in that the rotation axes of the two grinding spindles are perpendicular to a rotation axis of the disc spindle; wherein the grinding wheels comprise respective grinding surfaces, said grinding surfaces being substantially perpendicular to the rotation axis of the disc spindle and having a width (w.sub.1,w.sub.2) that is equal or greater than a width (w.sub.3) of the surface of the disc to be grinded, the width (w.sub.3) of the surface of the disc to be grinded being measured in a radial direction of the disc; and wherein the first grinding unit and the second grinding unit are configured to simultaneously move relative to the disc unit in an axis that is parallel to the rotation axis of the disc spindle and in opposite directions such that, in use, the grinding surfaces of the grinding wheels simultaneously contact opposite surfaces of the disc along the entire width (w.sub.3) of the surface (101a-b) of the disc to be grinded.

2. The machine tool according to claim 1, wherein the first grinding unit is mounted on a first platform and the second grinding unit is mounted on a second platform, the first and second platforms comprising means for moving the platforms relative to the at least one disc unit in an axis that is parallel to the rotation axis of the disc spindle and in opposite directions, respectively.

3. The machine tool according to claim 2, wherein the first platform and the second platform comprise respective spindles actuated by motors to move the platforms relative to the at least one disc unit.

4. The machine tool according to claim 2, wherein the at least one disc unit is fixedly mounted on a bench and the first and second platforms are movably mounted on the same bench.

5. The machine tool according to claim 1, wherein the first grinding spindle and the second grinding spindle are configured to rotate in the same direction or in opposite directions.

6. The machine tool according to claim 1, wherein the grinding spindles are cantilevered grinding spindles or twin-grip grinding spindles.

7. The machine tool according to claim 1, wherein the disc to be grinded is selected from a group comprising brake discs, circular knives and circular rotary blades.

8. The machine tool according to claim 1, wherein the first grinding unit comprises a first dresser comprising a first dressing tool that is configured to dress the first grinding wheel and the second grinding unit comprises a second dresser comprising a second dressing tool that is configured to dress the second grinding wheel.

9. The machine tool according to claim 8, wherein the dressers comprise: first means for moving the dressing tool in a direction perpendicular to the rotation axis of the grinding spindles and towards the grinding surfaces of the grinding wheels; and second means for moving, the dressing tool in a direction parallel to the rotation axis of the grinding spindles and along the width (w.sub.3) of the grinding wheels, the width (w.sub.3) of the grinding wheel being measured in a direction parallel to the rotation axis of the grinding spindles on the grinding surfaces.

10. The machine tool according to claim 8, wherein the dressers are stationary dressers or rotary dressers.

11. The machine tool according to claim 1, comprising: a first disc unit comprising a first disc spindle on which a first disc to be grinded is to be arranged and the third motor assembly for rotatably actuating the first disc spindle; a second disc unit comprising a second disc spindle on which a second disc to be grinded is to be arranged and a fourth motor assembly for rotatably actuating the second disc spindle; wherein the first grinding unit comprises two grinding wheels arranged on the first grinding spindle and the second grinding unit comprises two grinding wheels arranged on the second grinding spindle such that a first grinding wheel of the first grinding unit is located in correspondence with a first grinding wheel of the second grinding unit to simultaneously grind the first disc and a second grinding wheel of the first grinding unit is located in correspondence with a second grinding wheel of the second grinding unit to simultaneously grind the second disc.

12. The machine tool according to claim 11, comprising a dresser with a dressing disc located between the first and second grinding units, the dresser being movable in a direction parallel to the rotation axis of the grinding spindles such that a dressing surface of the dressing disc simultaneously contacts the grinding surfaces of the pairs of grinding wheels of the first and second grinding units located in correspondence, the dresser being configured to dress the grinding surfaces when the grinding wheels do not contact the discs.

13. A method for grinding discs with the machine tool according to claim 1, the method comprising the steps of: arranging a disc to be grinded in the disc spindle of the disc unit; actuating the disc spindle of the disc unit, the first grinding spindle of the first grinding unit and the second grinding spindle of the second grinding unit by the respective motor assemblies; simultaneously moving the first grinding unit and the second grinding unit in an axis that is parallel to the rotation axis of the disc spindle and in opposite directions towards the disc until the grinding surfaces of the grinding wheels simultaneously contact opposite main surfaces of the disc along the entire width of the main surfaces of the disc; simultaneously grinding both main surfaces of the disc by the grinding wheels of the first and second grinding units during a predefined period of time; simultaneously retracting the first and second grinding units; and removing the disc from the disc spindle of the disc unit.

14. The method of claim 13, comprising: actuating at least one of the first dressing tool and the second dressing tool of the first and second dressers, respectively; moving, by the first means, the corresponding dressing tool in a direction perpendicular to the rotation axis of the respective grinding spindles until a dressing surface of the dressing tool contacts the grinding surface of the grinding wheel; and moving, by the second means, the dressing tool in a direction parallel to the rotation axis of the grinding spindle and along the width (w.sub.1,w.sub.2) of the grinding wheel to dress its grinding surface, the width (w.sub.1,w.sub.2) of the grinding wheel being measured in a direction parallel to the rotation axis of the grinding spindle on the grinding surface.

15. The method of claim 13, comprising: arranging a first disc to be grinded in the first disc spindle of the first disc unit; arranging a second disc to be grinded in the second disc spindle of the second disc unit; actuating the disc spindles of the disc units by the respective motor assemblies, actuating a first grinding unit that comprises two grinding wheels arranged on the first grinding spindle and a second grinding unit that comprises two grinding wheels arranged on the second grinding spindle such that a first grinding wheel of the first grinding unit is located in correspondence with a first grinding wheel of the second grinding unit and a second grinding wheel of the first grinding unit is located in correspondence with a second grinding wheel of the second grinding unit; simultaneously moving the first grinding unit and the second grinding unit in an axis that is parallel to the rotation axes of the disc spindles and in opposite directions towards the discs until the grinding surfaces of the grinding wheels simultaneously contact opposite surfaces of the discs along the entire width of the surface of the disc; simultaneously grinding both surfaces of the discs by the grinding wheels of the first and second grinding units during a predefined period of time; simultaneously retracting the first and second grinding units; and removing the discs from the disc spindles of the disc units.

16. The machine tool according to claim 2, wherein the grinding spindles are cantilevered grinding spindles or twin-grip grinding spindles.

17. The machine tool according to claim 3, wherein the grinding spindles are cantilevered grinding spindles or twin-grip grinding spindles.

18. The machine tool according to claim 4, wherein the grinding spindles are cantilevered grinding spindles or twin-grip grinding spindles.

19. The machine tool according to claim 5, wherein the grinding spindles are cantilevered grinding spindles or twin-grip grinding spindles.

20. The machine tool according to claim 2, wherein the disc to be grinded is selected from a group comprising brake discs, circular knives and circular rotary blades.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] To complete the description and in order to provide for a better understanding of the invention, a set of drawings is provided. Said drawings form an integral part of the description and illustrate an embodiment of the invention, which should not be interpreted as restricting the scope of the invention, but just as an example of how the invention can be carried out.

[0048] The drawings comprise the following figures:

[0049] FIG. 1 shows a plant view of a machine tool for grinding a brake disc, according to an embodiment of the invention.

[0050] FIG. 2 shows a plant view of a machine tool for simultaneously grinding two brake discs, according to an embodiment of the invention.

[0051] FIG. 3 shows a plant view of a machine tool for grinding a brake disc including a diamond dresser for dressing each grinding wheel, according to an embodiment of the invention.

[0052] FIG. 4 shows a plant view of a machine tool for grinding two brake discs including one single diamond dresser, according to an embodiment of the invention

DETAILED DESCRIPTION OF THE INVENTION

[0053] FIG. 1 shows a plant view of a machine tool 100 for grinding a brake disc 101, according to an embodiment of the invention. It should be understood that the machine tool 100 of FIG. 1 may include additional components and that some of the components described herein may be removed and/or modified without departing from a scope of the described machine tool 100. Additionally, implementation of the machine tool 100 is not limited to such embodiment.

[0054] The machine tool 100 comprises a first grinding unit 102 mounted on a first platform 103, a second grinding unit 104 mounted on a second platform 105 and a brake disc unit 106 on which the brake disc 101 to be grinded is mounted. The first grinding unit 102 comprises a first grinding spindle 107, a first grinding wheel 108 arranged thereon and a first motor assembly 109 to rotatably actuate the first grinding spindle 107. The first grinding spindle 107 may rotate at a first peripheral speed r.sub.1, that for example may range between 100 and 5000 revolutions per minute, around a first rotation axis 110. The second grinding unit 104 comprises a second grinding spindle 111, a second grinding wheel 112 arranged thereon and a second motor assembly 113 to rotatably actuate the second grinding spindle 111. The second grinding spindle 111 may rotate at a second peripheral speed r.sub.2, that for example may range between 100 and 5000 revolutions per minute, around a second rotation axis 114. The rotation axes 110,114 of the first and second grinding spindles 107,111 are substantially parallel to each other. Preferably, both grinding wheels 108,112 will rotate in the same direction and with the same peripheral speed although they may rotate in opposite directions and at slightly different peripheral speeds.

[0055] The first platform 103 and the second platform 105 are movably mounted on a bench 115 while the brake disc unit 106 is fixedly mounted on said bench 115. For example, the first and second platforms 103,105 may include servomotors actuating ball screws, linear motors, or similar to move both platforms 103,105 in a direction that is substantially perpendicular to the rotation axes 110,114 of the first and second grinding spindles 107,111. The first platform 103 and the second platform 105 will move at a first speed v.sub.1 and a second speed v.sub.2, respectively, that will be preferably the same speed such that the grinding surfaces 108a, 112a of the first and second grinding wheels 108 112 simultaneously contact the braking surfaces 101a-b of the brake disc 101. The speeds v.sub.1 and v.sub.2 will vary depending on whether the grinding wheels are contacting the disc or they are not, and may range from 2000 mm/min when the grinding units are moving from their inoperative position to their operative position, to 0.001 mm/min during the grinding operation. By simultaneously contacting both braking surfaces 101a-b of the brake disc 101 deflections and loss of productivity that would be generated if the brake disc were grinded only on one side can be avoided.

[0056] The first and second grinding wheels 108,112 may be made of different material such as diamond (C), cubic boron nitride (cBN), silicon carbide (SiC), a combination of diamond and cBN, etc. The first and second motor assemblies 109,113 may be formed by direct spindle motors or AC motors with pulley or gear transmission and means for attaching the grinding units 102,104 to the first and second platforms 103,105, respectively. These means for attaching the grinding units 102,104 to the first and second platforms 103,105 may be, for example, a coupling structure that may be an integral part of the motor assemblies 109,113 or being couplable to said motor assemblies 109,113 and that could be welded or screwed to the platforms 103,105.

[0057] The brake disc unit 106 also has a brake disc spindle 116 on which the brake disc 101 is arranged and a third motor assembly 117 for rotatably actuating the brake disc spindle 116. The brake disc spindle 113 may rotate at a third rotational speed r.sub.3, that for example may range between 1 and 2000 revolutions per minute, around a third rotation axis 118. The third rotational speed r.sub.3 may be equal or different to the first and second rotational speeds r.sub.1, r.sub.2. The third motor assembly 116 may also be formed by a servomotor or stepper motor and means for attaching the brake disc unit 106 to the bench 115. Similarly, these means for attaching the brake disc unit 106 to the bench 115 may be, for example, a coupling structure that may be an integral part of the motor assembly 117 or being couplable to said motor assembly 117 and that could be welded or screwed to the bench 115. The rotation axes 110,114 of the two grinding spindles 108,111 are substantially perpendicular to the rotation axis 118 of the brake disc spindle 116.

[0058] The grinding surfaces 108a,112a of the grinding wheels are substantially planar and perpendicular to the rotation axis 118 of the brake disc spindle 116. These grinding surfaces 108a,112a have a width w.sub.1, w.sub.2 that is equal or greater than the width w.sub.3 of the braking surfaces 101a-b of the brake disc 101. The width of the braking surfaces 101a-b is measured in the radial direction of the brake disc 101. In turn, the width of the grinding surfaces 108a,112a is measured in a direction parallel to the rotation axes 110,114 of the grinding spindles 107,111.

[0059] FIG. 1 shows the two grinding units 102,104 in their inoperative position in which the grinding wheels 108,112 does not contact the braking surfaces 101a-b of the brake disc 101 and they are positioned far away from it. In use, the platforms 103,105 move relative to the bake disc unit 106 such that the grinding units 102,104 are in their operative position, i.e., the grinding wheels 108,112 displace relative to the brake disc unit 106 in a direction that is perpendicular to the brake disc 101 until the grinding surfaces 108a,112a contact the respective braking surfaces 101a-b along their entire width. The material removal from the brake disc 101 by the abrasive grinding wheels 108,112 is caused by the relatively high tangential peripheral speed between the grinding wheels 108,112 and the brake disc 101, in combination with the relative perpendicular feed motion of the grinding wheels 108,112 relative to the brake disc 10. The tangential material removal mechanism due to the tangential peripheral speed of the grinding wheels 108,112 relative to the brake disc 101 reduces the temperature reached on the braking surfaces 101a-b during grinding operation.

[0060] Thus, plastic deformations, cracks and wear in the brake discs 101 are avoided or at least minimized. Besides, by having grinding surfaces 108a,112a whose width w.sub.1, w.sub.2 is equal or greater than the width w.sub.3 of the braking surfaces 101a-b of the brake disc 101 there is no need to move the grinding wheels 108,112 in a direction that is perpendicular to the rotation axes 110,114 of the disc spindles 107,111 during the grinding operation, avoiding creating contouring marks on the main surfaces of the brake disc 101 that may worse its braking properties. The combination of the perpendicular movement of the grinding wheels 108,112 relative to the brake disc 101 with the grinding wheels 108,112 having a width w.sub.1, w.sub.2 that is equal or greater than the width w.sub.3 of the surface 101a-b of the brake disc 101 to be grinded reduces the time required to grind the braking surfaces 101a-b which increases the productivity and efficiency of the resurfacing process. It also avoids creating contouring marks on said braking surfaces 101a-b that may worse the braking properties of the disc 101.

[0061] The combination of the perpendicular movement of the grinding wheels 108,112 relative to the brake disc 101 with the grinding wheels 108,112 having a width w.sub.1, w.sub.2 that is equal or greater than the width w.sub.3 of the surface 101a-b of the brake disc 101 to be grinded reduces the time required to grind the braking surfaces 101a-b which reduces the temperature reached in said surfaces 101a-b and increases the productivity and efficiency of the resurfacing process.

[0062] While FIG. 1 shows the disc unit 106 with a brake disc 101 arranged thereon, another disc-shaped piece such as a circular knife or circular rotary blades may be coupled to the disc spindle 116 of the disc unit 106.

[0063] FIG. 2 shows a plant view of a machine tool 200 for simultaneously grinding two brake discs 201,219, according to an embodiment of the invention. It should be understood that the machine tool 200 of FIG. 2 may include additional components and that some of the components described herein may be removed and/or modified without departing from a scope of the described machine tool 200. Additionally, implementation of the machine tool 200 is not limited to such embodiment.

[0064] The machine tool 200 of FIG. 2 is essentially the same machine tool 100 of FIG. 1 but where the first grinding spindle 207 comprises a first grinding wheel 208 and a second grinding wheel 220 arranged thereon and the second grinding spindle 211 comprises a third grinding wheel 212 and a fourth grinding wheel 221 arranged thereon, and having two brake disc units 206,221 fixedly arranged on the bench 215.

[0065] The machine tool 200 comprises a second brake disc unit 222 having a brake disc spindle 223 on which the second brake disc 219 is arranged, e.g., clamped, and a fourth motor assembly 224 for rotatably actuating the brake disc spindle 223. The brake disc spindle 223 may rotate at a fourth rotational speed r.sub.4, that for example may range between 1 and 2000 revolutions per minute, around a fourth rotation axis 225. The fourth rotational speed r.sub.4 may be equal or different to the third rotational speed r.sub.3 of the other brake disc unit 206. The fourth motor assembly 224 may also be formed by a stepper motor, servomotor or similar, and means for attaching the second brake disc unit 222 to the bench 215. These means for attaching the brake disc unit 222 to the bench 215 may be, for example, a coupling structure that may be an integral part of the motor assembly 224 or being couplable to said motor assembly 224 and that could be welded or screwed to the bench 215. The rotation axis 218,225 of the two brake disc spindles 216,223 are substantially parallel to each other. The operation of the machine tool 200 of FIG. 2 is the same than the operation of the machine tool 100 of FIG. 1.

[0066] In this way, the first grinding wheel 208 is located in correspondence with the fourth grinding wheel 221 to simultaneously grind the first brake disc 201 and the second grinding wheel 220 is located in correspondence with the third grinding wheel 212 to simultaneously grind the braking surfaces 201a-b,219a-b of the first and second brake discs 201,219, respectively. This architecture allows grinding two brake discs at the same time increasing the productivity rate of the machine tool 200.

[0067] While the machine tool 200 of FIG. 2 shows the two brake discs 201,219 having the same width w.sub.3, and thus, the four grinding wheels have also the same widths, the two brake discs 201,219 may have different widths and thus, the pairs of grinding wheels 208,221 and grinding wheels 212,220 may have a different width, each of these widths being adapted to grind the corresponding brake disc.

[0068] FIG. 3 shows a plant view of a machine tool 300 for grinding a brake disc 301 including a diamond dresser 326 for dressing each grinding wheel 308,312, according to an embodiment of the invention. It should be understood that the machine tool 300 of FIG. 3 may include additional components and that some of the components described herein may be removed and/or modified without departing from a scope of the described machine tool 300. Additionally, implementation of the machine tool 300 is not limited to such embodiment.

[0069] The machine tool 300 of FIG. 3 is essentially the same machine tool 100 of FIG. 1 but including the diamond dressers 326 for dressing the grinding surfaces 308a,312a of the grinding wheels 308,312. The dressing operation is carried out by the diamond dressers 326 when the grinding units 302,304 are in their inoperative position. The diamond dressers 326 are mounted on corresponding platforms 327a-b which are actuated by respective servomotors (not shown in this figure) to move the diamond dressers 326 from an inoperative position in which the diamond dressers 326 do not contact the grinding surfaces 308a,312a and they are positioned far away from the grinding wheels 308,312 and an operative position in which the diamond dressers 326 contact the grinding surfaces 308a,312a to dress them. Specifically, each diamond dresser 326 comprises a first platform 327a configured to move the diamond dressers 326 in a direction that is perpendicular to rotation axes 310,314 of the grinding spindles 307,311 and a second platform 327b to move the diamond dressers 326 in a direction that is parallel to rotation axes 310,314 of the grinding spindles 307,311.

[0070] In such embodiments, the diamond dressers 326 are mounted on the platforms 303,305 and are located in correspondence with a plane formed by both grinding wheels rotational axes and behind the grinding wheels 308,312. Moreover, the diamond dresser comprises a diamond 328 to dress the grinding surfaces 308a,312a of the grinding wheels 308,312.

[0071] The platforms 327a are configured to, once the grinding wheels 308,312 are in their inoperative position, move the diamond dresser 326 in a direction that is perpendicular to rotation axes 310,314 of the grinding spindles 307,311 until the diamond 328 contacts the grinding surfaces 308a,312a of the grinding wheel 308,312. Then, the platforms 327b are configured to move the diamond dresser 326 in a direction that is parallel to rotation axes 310,314 of the grinding spindles 307,311 along the entire width of these grinding surfaces 308a,312a to dress them. Alternatively, this dressing operation may be carried out by the diamond dressers 326 during the grinding operation of the grinding wheels 308,312, i.e., when they are in their operative position.

[0072] FIG. 4 shows a plant view of a machine tool 400 for grinding two brake discs (not shown in this figure) including one single diamond dresser 429, according to an embodiment of the invention. It should be understood that the machine tool 400 of FIG. 4 may include additional components and that some of the components described herein may be removed and/or modified without departing from a scope of the described machine tool 400. Additionally, implementation of the machine tool 400 is not limited to such embodiment.

[0073] The diamond dresser 429 comprises a diamond dressing disc 430 mounted on a dressing spindle 431 that is actuated by a servomotor 432 and it is mounted on a platform 433 that is configured to move in a direction that is substantially parallel to the rotation axes 410,414 of the grinding spindles 407,411.

[0074] In such embodiment, the two grinding units 402,404 move to a dressing position that is generally located at an intermediate point between their operative and inoperative positions. When the two grinding units 402,404 are positioned in their dressing position, the distance between the two closest points of their grinding surfaces is substantially equal to the diameter of the diamond dressing disc 430. Then, the diamond dresser 429 is configured to move in a direction that is substantially parallel to the rotation axes 410,414 of the grinding spindles 407,411 until it contacts the grinding surfaces 420a,412a of the grinding wheels 420,412 and continuous with the movement along the entire width of the surfaces 420a,412a until said grinding surfaces 420a,412a have been completely dressed. After that, the diamond dresser 429 is configured to carried out the same operation for dressing the surfaces 408a,421a of the grinding wheels 408,421.

[0075] The architecture and disposition of the diamond dressers of FIGS. 3 and 4 is interchangeable. That is to say, the machine tool 300 of FIG. 3 may incorporate one single dresser placed between both grinding units and being movable in a direction that is substantially parallel to the rotation axes of the grinding spindles and the machine tool 400 of FIG. 4 may comprise one dresser for each one of the grinding wheels as in FIG. 3. Besides, the dressers shown in FIGS. 3 and 4 may be stationary dressers or rotary dressers with dressing tools made of different abrasive materials.